The UCSF Immunology Training Program encompasses 43 laboratories engaged in molecular and cellular immunology and actively training graduate and postdoctoral scientists. Areas of active research include lymphocyte cell surface receptor structure, signaling mechanism, and immune system function, histocompatability antigen expression and intracellular trafficking, roles of receptors and antigen specificity in lymphocyte development, lymphocyte and leukocyte cell adhesion molecule structure and function, immunoglobulin gene hypermutation and class-switch recombination, cytokine expression, mechanisms of autoimmunity, allergy, and defense against infectious agents, and various aspects of AIDS including pathogenesis, HIV interaction with lymphocytes, and mechanisms of HIV viral gene expression and genome packaging. Over the past 24 years, a vital graduate training program leading to the Ph.D. has been developed by the immunology program faculty and has been supported by this training grant for the past 20 years. This program is designed to provide a solid background in genetics, cell biology, molecular biology, and mammalian tissue and organ biology as well as thorough training in molecular and cellular immunology. The interdisciplinary nature of this training is enhanced by the affiliation of the Immunology Program with the UCSF Biomedical Sciences Program (BMS), an interdisciplinary program that also includes the study of infectious agents and inflammatory processes as well as other aspects of mammalian tissue/organ development, function, and disease. In addition to formal coursework and thesis research, the Immunology Program includes an active weekly seminar series of outside immunology speakers, both Immunology and BMS student-faculty journal clubs, an annual Immunology Program conference (held jointly with UC Berkeley immunologists), and seminar courses on advanced immunological topics. These activities provide an excellent training environment for postdoctoral fellows as well as for graduate students. Postdoctoral training is additionally enhanced by a postdoc research-in-progress seminar series and a new postdoctoral mentoring program.